160 meter antennas that work well near metal roofs?

[JasonW]

Hello All,I recently came across this design for a top-loaded folded vertical attic antenna for 160 meters: www.qsl.net/g3pto/roofant.htmlMy log house has a corrugated metal roof, so suspending it in the attic just under the roof peak obviously isn't a good option.However, would the antenna work acceptably well if it were strung along the non-metallic ceiling about 12 feet below the roof peak? The vertical portion at the feed end could be continued down into the wood-crib basement to the transceiver, and a counterpoise wire or chicken wire ground screen could be installed in the basement. (The insulated top-loading wires would be run under the carpet along the wooden first floor.)Many thanks in advance to anyone who can help. -- Jason

 

[Ham]

Re: metal roofs work as 160 meter antennas

Hard to say without seeing the facility but here's a thought.Could you use the metal roof as the antenna? Of course you'll need a "match box" to match the roof with your radio. Good luck,73

 

[JasonW]

I had considered that, but the corrugated metal panels aren't continuous from the roof peak to the bottom edge of the roof; they are overlapped like shingles.If they were one-piece from peak to bottom edge, I'd connect them all together with wires at the bottom edge of the roof. As they are, with no good electrical contact between the overlapping panels (they're coated with a green compound), their contact points would probably become rectifiers and cause RFI all over the neighborhood if I tried to load up the metal roof as an antenna. The poor inter-panel electrical continuity would also make the metal roof problematic at best even for use as a ground plane. -- Jason

 

[Neal]

However if you could Put up a 70-80 foot Rohn 25 tower make a Unipole... and use the Roof as an Elevated Ground system... Buried Ground systems are usually 120 radials but Elevated radials up about 10 feet off the Ground you Only need 4-6 radials...Neal-ka2caf

I had considered that, but the corrugated metal panels aren't continuous from the roof peak to the bottom edge of the roof; they are overlapped like shingles.If they were one-piece from peak to bottom edge, I'd connect them all together with wires at the bottom edge of the roof. As they are, with no good electrical contact between the overlapping panels (they're coated with a green compound), their contact points would probably become rectifiers and cause RFI all over the neighborhood if I tried to load up the metal roof as an antenna. The poor inter-panel electrical continuity would also make the metal roof problematic at best even for use as a ground plane. -- Jason

 

[4dude]

160 is alot like the regular AM band is it not?? (.53 to 1.7Mhz)During the day for instance 1.08 from hartford travels about 150 Miles or so.......(I get them fine here in Upstate NY all day)How good is 160 during the day?? Can you get 300Miles on Sideband? (During the day) and how good are the AM conditions on 160 during the day??Just kinda wondering about 160 a little bit

 

[JasonW]

*Sigh* I'd love to put up a tower, but on this small lot even a 30' tower could fall across power lines on either side if it toppled. -- Jason

However if you could Put up a 70-80 foot Rohn 25 tower make a Unipole... and use the Roof as an Elevated Ground system... Buried Ground systems are usually 120 radials but Elevated radials up about 10 feet off the Ground you Only need 4-6 radials...Neal-ka2caf

I had considered that, but the corrugated metal panels aren't continuous from the roof peak to the bottom edge of the roof; they are overlapped like shingles.If they were one-piece from peak to bottom edge, I'd connect them all together with wires at the bottom edge of the roof. As they are, with no good electrical contact between the overlapping panels (they're coated with a green compound), their contact points would probably become rectifiers and cause RFI all over the neighborhood if I tried to load up the metal roof as an antenna. The poor inter-panel electrical continuity would also make the metal roof problematic at best even for use as a ground plane. -- Jason

 

[JasonW]

As I'm still working toward my Ham ticket I'm no authority on the subject, but as a long-time AM broadcast band DXer I can tell you that vertical polarization (for transmitting and receiving) results in ground wave propagation ranges such as those that you mentioned, if the AM station is running sufficient power.The 160 meter Ham band extends from 1.8 MHz - 2.0 MHz, so its propagation characteristics are very similar to those of AM broadcast band signals.For local 160 meter coverage comparable to that of an AM radio station, a vertically-polarized antenna radiating via ground wave propagation works well. A Marconi "Tee" wire antenna works well for this. Most 160 meter operators aren't running as much power as AM stations (except perhaps 250 watt AM daytimers), nor are most 160 meter vertical antennas large enough (or equipped with really good radial systems, due to space constraints) to radiate as efficiently as AM towers. However, most 160 meter operators use large (if not full-size) outdoor antennas for receiving, which compensates for the lower transmission power levels.Low-mounted 160 meter dipoles can be used for NVIS (Near-Vertical Incidence Skywave) propagation out to a few hundred miles, and mounting such a dipole higher will make it useful for long-distance contacts via ionospheric skip. A short, coil-loaded or capacitive "top-hat"-loaded vertical antenna with a high angle of radiation can also be used for contacts via ionospheric skip. -- Jason

160 is alot like the regular AM band is it not?? (.53 to 1.7Mhz)During the day for instance 1.08 from hartford travels about 150 Miles or so.......(I get them fine here in Upstate NY all day)How good is 160 during the day?? Can you get 300Miles on Sideband? (During the day) and how good are the AM conditions on 160 during the day??Just kinda wondering about 160 a little bit

 

[Neal]

Ok Jason on the lot size.. but can you mount a mobile antenna like a hustler with a 160 coil or a texas bug catcher and ues the roof as the ground plane... Either of those would be my next choice for 160... they work Mobile why not for base. however the bandwidth is very narrow so pick 1 or 2 frequencys close to each other like 1880 and 1885 and your set. Neal-ka2caf

*Sigh* I'd love to put up a tower, but on this small lot even a 30' tower could fall across power lines on either side if it toppled. -- Jason

However if you could Put up a 70-80 foot Rohn 25 tower make a Unipole... and use the Roof as an Elevated Ground system... Buried Ground systems are usually 120 radials but Elevated radials up about 10 feet off the Ground you Only need 4-6 radials...Neal-ka2caf

I had considered that, but the corrugated metal panels aren't continuous from the roof peak to the bottom edge of the roof; they are overlapped like shingles.If they were one-piece from peak to bottom edge, I'd connect them all together with wires at the bottom edge of the roof. As they are, with no good electrical contact between the overlapping panels (they're coated with a green compound), their contact points would probably become rectifiers and cause RFI all over the neighborhood if I tried to load up the metal roof as an antenna. The poor inter-panel electrical continuity would also make the metal roof problematic at best even for use as a ground plane. -- Jason

 

[w9wi]

- The QRM (interference) levels on the 160-meter ham band are FAR, FAR less than in the AM BCB. A relatively weak signal "carries" surprisingly far (either on 160 or on the BCB) if there aren't dozens of other signals interfering with it. (remember the early days of the expanded band?)- Groundwave propagation gets worse (quickly) with increasing frequency. One chart suggests a 1kw signal on 550 has the coverage of 50kw on 1550; the groundwave is even worse on 160 meters. But hams almost always work with skywave, which gets *better* with increasing frequency.- Unlike the BCB, there are no FCC regulations for minimum antenna efficiency and ground systems for amateurs. In fact, few if any amateurs have antennas that would comply with the regulations for BCB stations. [0] As a result, amateur stations usually have a much poorer groundwave signal for the available power [1] than broadcast stations. On the other hand, due to the poorer ground the skywave signal is usually better. - Amateur stations almost exclusively use either Morse Code or single-sideband transmission on 160 meters. These modes are considerably more efficient than regular AM. Anyway, the result is that a modest amateur station can cover hundreds if not thousands of miles on 160 meters. My best "DX" on the band is Kure Island, on the western end of the Hawaiian chain, worked at a time when my 500-watt amplifier was working. Right now, it isn't -- but I still received a "heard" card from England last November... and hear more powerful European stations all the time.[0] the rare exception usually being when an amateur is able to borrow the antenna system of a daytime-only BCB station![1] Ironically, many amateur stations have *more* power than many smaller BCB stations. The legal limit is 1,500 watts.

 

[Neal]

Lets get this correct... remember I am talking Carrier power. that 1500 watts is Plate dissipationits actually a legal limit of 375 watts carrier.. or there abouts

[1] Ironically, many amateur stations have *more* power than many smaller BCB stations. The legal limit is 1,500 watts.

 

[4dude]

Very interesting reading

 

[JasonW]

<Ok Jason on the lot size.. but can you mount a mobile antenna like a hustler with a 160 coil or a texas bug catcher and ues the roof as the ground plane... Either of those would be my next choice for 160... they work Mobile why not for base. however the bandwidth is very narrow so pick 1 or 2 frequencys close to each other like 1880 and 1885>Can those 160 meter mobile antennas pass a 5 kHz or 10 kHz signal? I'm mostly interested in AM phone mode operation. -- Jason

 

[4dude]

AM rocks on ANY BAND!!!!!! (FM is good also)Whats the farthest you have ever talked on FM jason??

 

[JasonW]

AM rocks on ANY BAND!!!!!! (FM is good also)Whats the farthest you have ever talked on FM jason??

If you're referring to 88 MHz - 108 MHz, I'm afraid I'll have to plead the 5th on that one (I don't do that anymore, and it was a long time ago). Before that I occasionally operated a homebrew damped wave (spark gap) transmitter, which is also long gone.Other than that, legal power 11 meter AM and Part 15 AM (510 kHz - 1700 kHz) are all I've ever used. -- Jason

 

[4dude]

oops,thought you were an HF guy...Ah man!!

 

[JasonW]

oops,thought you were an HF guy...Ah man!!

I'm working toward my Ham ticket so that I can legally get on HF, MF, and LF (the new experimental 600 meter band at 495 kHz - 510 kHz http://500kc.com ). I haven't engaged in the above-mentioned "extra-curricular activities" for decades and I never will again--I know that I was just *very* lucky to have never been caught. Believe me, radio is a *lot* more fun when you're not forever worrying about being DF'ed and getting the dreaded knock on the door... -- Jason

 

[4dude]

Ah man!!I hear ya my friend I didnt know about that 600Meter band....Thats interesting,im gonna take a gander @ that site you provided

 

[fatman]

As far as using mobile antennas at home... why not try a full size screwdriver antenna? You can adjust it for all bands, it's small, doesn't require a tower and I would suspect that metal roof would make a great ground plane. I use the Little tarheel on my Grand CHarokee and if I can hear them I can probably contact them. These antennas are a great all band, no tuner required antenna because the infinite adjustment makes the tuner unnecessary. I like the Tarheel antennas (www.tarheelantennas.com) but there are many others out there.Another advantage of the screwdriver antenna over the Hustler or Hamstick variety is the fact that you change bands and fine tune via a rocker switch at the operating position rather than going outside to change whips or resonaters. I used an Outbacker antenna for a while and it was a great antenna (confirmed 100 watt 20 meter mobile contact from Mississippi to Antarctica). The only problem is that I was stuck on one band if I didn't feel like pulling over and changing the tap. No more of that with the screwdriver on the car now.Good luck and 73,DonAE5DW

 

[JasonW]

Don, I thank you for this suggestion. All the way to Antarctica? Not bad for a "leaky dummy load," eh? You know, this just might work as a roof-mounted antenna even here in interior Alaska (-50 degrees isn't uncommon in the winter). I could put the antenna inside a white PVC pipe "radome" and use a heating strip or a light bulb to keep the screwdriver tuning mechanism warm enough, if necessary. -- Jason

 

[Neal]

log cabin in Alaska? WOW you lucky dog.. my dream house is a log cabin Been looking for 2 years now Just way to expensive

Don, I thank you for this suggestion. All the way to Antarctica? Not bad for a "leaky dummy load," eh? You know, this just might work as a roof-mounted antenna even here in interior Alaska (-50 degrees isn't uncommon in the winter). I could put the antenna inside a white PVC pipe "radome" and use a heating strip or a light bulb to keep the screwdriver tuning mechanism warm enough, if necessary. -- Jason